The present application claims priority to Japanese Application No. P11-082367 filed Mar. 25, 1999 which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
This invention relates to a method of manufacturing a thin film magnetic head prepared by laying the components of the head device to produce a multilayer structure by means of a thin film forming process. More particularly, it relates to a method of manufacturing a thin film magnetic head having an upper layer pole for restricting the track width.
2. Prior Art
A magnetic head as described herein refers to a head typically mounted on a magnetic recording/reproducing apparatus such as a hard disk apparatus in order to record a recording signal to and/or reproduce a recording signal from a magnetic recording medium. A bulk-type magnetic head prepared by winding a wire coil around a magnetic core is typically used for such a magnetic head. However, a bulk-type magnetic head provides certain limits to micro-machining operations and it is difficult to down-size the magnetic head in order to make it adapted to high density signal recording.
In an attempt for avoiding this problem, there have been proposed so-called thin film magnetic heads prepared by way of a thin film forming process of sequentially laying a lower core layer, a non-magnetic layer and an upper core layer on a substrate to form a multilayer structure. Such a thin film magnetic head can be down-sized and is still adapted to high density signal recording because the components of the head are formed through a thin film forming process.
When preparing a thin film magnetic head, an upper layer pole is formed at an end of the sliding surface thereof where a magnetic recording medium is to be slid before forming the upper core layer on the non-magnetic layer. As a result, the width of the track to be used for signal recording/reproduction is defined by the upper layer pole of the thin film magnetic head so that it can be accurately and finely finalized.
When forming the upper layer pole, firstly a plating underlay film is formed on the non-magnetic layer lying on the lower core layer and then a frame-like photoresist layer is formed on the plating underlay film. Subsequently, a plating operation is conducted and the photoresist layer is removed to produce the upper layer pole.
Meanwhile, there is an ever-increasing demand for thin film magnetic head showing a smaller track width that by turn meets the demand for high recording density in recent years. However, since the plating solution for forming the upper layer pole by means of the above described known thin film magnetic head manufacturing method is hydrophobic in terms of resist, there is an insurmountable limit for the attempt of reducing the track width by reducing the width of the upper layer pole. A technique of chemically coarsening the surface of the resist layer may be used to improve the hydrophilicity thereof before proceeding to the plating operation in the step of forming the upper layer pole with the above known manufacturing method, it has been nonetheless impossible to reduce the minimal width of the upper layer pole to less than 1 xcexcm if the accuracy of the chemical composition and that of the dimensions of the upper layer pole are to be held to a satisfactory level.
In an attempt for further reducing the minimal width of the upper layer pole, two techniques have been proposed to date as described below. With the first proposed technique, after forming the upper layer pole, it is trimmed by means of an FIB (focussed ion beam). With the second proposed technique, after forming a relatively wide upper layer pole, it is trimmed by etching it from the sliding surface thereof where a magnetic recording medium is to be slid, using a mask pattern in the slider-processing step.
However, with the first proposed technique, since a large number of thin film magnetic heads formed on a common substrate have to be treated on a one by one basis, it is difficult to improve the precision level of treating the thin film magnetic heads in terms of dimensions and profile and that of aligning the recording head and the reproducing head laid one on the other for the thin film magnetic head. Additionally, the first proposed technique is rather time consuming and hence it is difficult to improve the productivity of manufacturing magnetic heads with the technique. More specifically, if the processing time per thin film magnetic head is 10seconds and a total of 7,000 thin film magnetic heads are formed on a single common substrate, about 20 hours will be required to process all the thin film magnetic heads.
On the other hand, with the above described second technique, it is difficult to improve the precision level of aligning a mask formed on a head rover and reproducibility of the accuracy of the mask profile in the slider processing step. Additionally, with the second technique, the surface a magnetic recording medium is to be slide shows a U-shaped cross section. Thus, foreign objects can become deposited in the recess of a magnetic head prepared with the second technique to eventually corrode the upper layer pole.
In view of the above described circumstances, it is therefore the object of the present invention to provide a method of manufacturing a thin film magnetic head adapted to high density recording by forming the upper layer that defines the track width with an enhanced level of precision in terms of the width and also adapted to improve the manufacturing productivity.
According to the invention, the above object is achieved by providing a method of manufacturing a thin film magnetic head by sequentially forming at least a lower core layer, a non-magnetic layer and an upper core layer having an upper layer pole defining the track width on a substrate and subsequently forming a magnetic gap between said lower core layer and said upper layer pole, said method comprising:
an upper layer pole forming step of forming a lower core layer and a non-magnetic layer on a substrate and forming an upper layer pole thereon with a profile wider than the designed track width;
a first etching step of forming a first mask covering one of the lateral sides of said upper layer pole along the track and etching the other lateral side exposed from the mask; and
a second etching step of forming the lateral side etched in said first etching step and etching the lateral side opposite to it;
said upper layer pole being made to have the intended track width.
With the above described method of manufacturing a thin film magnetic head, the upper layer pole for defining the track wide can be formed with an enhanced level of dimensional accuracy particularly in terms of the width along the track. Additionally, since the profile of the upper layer pole is finely treated by etching, a large number of thin film magnetic head formed on a single common substrate can be treated at the same time.
As described above, with a method of manufacturing a thin film magnetic head according to the invention, it is possible to form the upper layer pole with an enhance level of dimensional accuracy particularly in terms of the width along the track by sequentially etching the two lateral sides of the upper layer pole along the track. Additionally, since the profile of the upper layer pole is treated in a resist film forming step and an etching step, a large number of thin film magnetic heads formed on a single common substrate can be treated at the same time. Thus, with a method of manufacturing a thin film magnetic head according to the invention, it is now possible to manufacture a large number of high precision thin film magnetic heads adapted to high density recording on a mass production basis.